$\mathrm{{\rm Y}}(1s)\to \gamma f_2(1270)$ Decay

Decay $\mathrm{{\rm Y}}(1s)\to \gamma f_2(1270)$ is studied by an approach in which the tensor meson, $f_2(1270)$, is strongly coupled to gluons. Besides the strong suppression of the amplitude $\mathrm{{\rm Y}}(1s)\to \gamma gg,gg\to f_2$ by the mass of b-quark, d-wave dominance in $\mathrm{{\rm Y}}(1s)\to \gamma f_2(1270)$ is revealed from this approach, which provides a large enhancement. The combination of these two factors leads to larger $B(\Upsilon(1s)\to\gamma f_2(1270))$\mathrm{.}Thedecayrateof$\Upsilon(1s)\to\gamma f_2(1270)$ and the ratios of the helicity amplitudes are obtained and they are in agreement with data.